Corrosion stability of cerium-doped cataphoretic epoxy coatings on AA6060 alloy

Abstract

In this study, corrosion protection efficiency of undoped epoxy and epoxy coating doped with cerium on aluminum alloy AA6060 is evaluated over prolonged exposure to 3 wt% NaCl solution by electrochemical impedance spectroscopy (EIS). Different amounts of Ce(NO3)3 are added into the epoxy suspension used for the cataphoretic deposition. Suspension stability is characterized by zeta potential and particle size values. Water content and thermal stability of the coatings were determined by thermogravimetric analysis. Insufficient corrosion stability, very close to that of undoped epoxy, is revealed for the coating with 1 mM Ce. Higher cerium doping contributes to a significant increase in corrosion stability (2–3 orders of magnitude greater charge‐transfer resistance). Epoxy coating doped with 5 mM Ce displays a pronounced self‐healing ability and the best corrosion protection and adhesion, owing to evenly distributed cerium precipitates on the aluminum surface. In the case of 10 mM Ce‐doped coating, the formation of Ce clusters and higher porosity causes a certain lowering of the protective ability. EIS measurements on epoxy coating with artificial defect confirm these findings.

EIS investigation of a Ce‐based posttreatment step on the corrosion behaviour of Alclad AA2024 anodized in TSA

“…Using a simulated scratch‐cell wherein bare AA2024‐T3 was exposed together with a sample protected by the Zr‐Ce conversion coating to the same electrolyte, the authors documented increased impedance response of the bare sample with immersion time, which was associated with the precipitation of Ce‐oxide at cathodic sites . Finally, several works in the literature report self‐healing abilities for different coatings when modified with Ce ions …”

“…30 Finally, several works in the literature report self-healing abilities for different coatings when modified with Ce ions. [31][32][33][34] In the present study, the effect of a posttreatment step consisting of immersion in solutions containing Ce ions on the microstructure and the corrosion resistance of clad AA2024-T3 anodized in TSA was investigated. In addition to improving the corrosion resistance of the system, the treatment aims to create a reservoir of Ce-ions which could impart corrosion inhibiting properties (self-healing) to an anodized layer that, in future investigations, will be further protected by coatings (primer and top coating).…”

Corrosion characteristics of laser-cleaned surfaces on iron artefact

“…The pore resistance value R p remains practically constant throughout the entire testing period (Figure 8a). The corrosion reactions (processes) under the Paraloid coating lead to the loss of adhesion and to partial delamination of the coating (Figure 8b) [31][32][33].…”

Corrosion behaviour of AA2024 aluminium alloy in different tempers in NaCl solution and with the CeCl3 corrosion inhibitor

“…Cerium belongs to the group of cathodic corrosion inhibitors for aluminium alloys. A large number of papers deal with the study of the inhibitory effect of cerium in the AA2024 alloy …”